The fourth episode in the history of plant
evolution is marked by the emergence of flowering plants during the early
Cretaceous period in the Mesozoic era, about 130 million years ago. The major
difference of these new plants, or angiosperms, contrasted to gymnosperms,
resides in the complexity of the reproductive structure. This new structure
includes a flower bearing seed within protective chambers, called ovaries, as
opposed to the naked seed that gymnosperms produce. The majority of modern
plant species are represented by angiosperms, or flowering plants.